Chip drying furnace



Nov. 24, 1931. F. H. LONGYEAR CHIP DRYING FURNACE Filed Aug. 11, 1930 2 Sheets-Shet 1 INVENTOR ATTORNEY Nov. 24, 1931. F. H. LONGYEAR CHIP DRYING FURNACE Filed Aug. 11, 1930 2 Sheets-Sheet 2 INVENTOR flank H- A onyyean Patented Nov. 24, 1931 UNITED {STA S PATENT OFFICE FRANK H. LONGYEAR, OF DETROIT, MICHIGAN, ASSIGNOR TO THERMAL ENGINEERING CORPORATION, OEDETROIT, MICHIGAN A COBTORATION OF MICHIGAN can? nnvme'rnmvacn 7 Application filed August 11, ,1930." Serial No. 474,525.

This invention relates to furnaces and more particularly to a chipdrying furnace and has as its objects to simplify, render more eflicient and improve generally devices of this character.

The invention has as one of its objects to provide a furnace designed to remove oil,

water, moisture or cutting compound having oil as a base, from the surface of metallic chips. b r nsrsturnings, etc., of brass, aluminum, steel. iron and the like. The furnace may be used with equal facility for removing oil, water. etc., from small fabricated parts and the like. i

In carrying out my invention the chips, fabricated parts" or the like are conducted through a heated chamber and also subjected to direct flame impingement without injury to the metal due to oxidation.

My improved chip drying furnace consists of a furnace structure having primary and secondary combustion chambers. the former being provided with gas or fuel burners aranged for direct impingement of the flame upon the material passing therethrough. Screw conveyors are provided for conveying the material to be treated horizontally through the furnace and the material isthereafter delivered to a vertical conveyor and subsequently discharged. The furnace structure contem lates the provision of a sec ondary air manifold and pilot light for utilizing the vapors or gases given off dueto he a i ization of the oil to promote com bustion in the secondary chamber thereby decreasing the amount of fuel used by the burners in, the primary chamber. Manv advantages are realized from the'use of a chip dryingfurnace,particularlv where magnetic separation of the chips is prac-' ticed. For instance, chips free from oil permit the separator to removenot only the,

larger pieces of metal but also the dust which in wet or moist chips, is held fast to the turnings by the moisture present. Dry chips permit a more even distribution of the chips through the separator and eliminate the possibility of picking up non-magnetic material by the magnetic separator :Asa result a better product is obtainable for introduction into the melting furnace. i NVhere the chips are charged directly into the melting furnace the time heretofore required to permit the oil to burn off before the" melting operation is started is eliminated and experience has shown that dry chips melt down considerably faster than those in which moisture is present when charged. Moreover, from the metallurgical standpoint the presence of oil, especially in metals as they are melted, is undesirabl The several objects, advantages and novel details of construction of my invention will be made more apparent as this description proceeds, especially when considered in connection with the accompanying drawings, wherein.

Figure 1 is a longitudinal sectional elevatio'nal view through a furnace constructed in accordance with my invention, and

Figure 2 is a vertical transverse sectional view taken substantially on the plane indicated byline g2-2in Figure 1.

ricated from refractory brick and steel, the reference character 10 indicating the bottom thereof which is supported and reinforced by longitudinally extending I beams 11 and cross members 12, the longitudinal members being mounted on a foundation indicated generally by the referencecharacter 13.

The top 14 of the furnace is of refractory brick suitablyreinforced as are also the end walls '15 and 16. The reference character 17 indicates the side walls of the furnace;

Extending transversely of the furnace between the side wa1ls;17' and arranged subst'antially intermediate the length of the .fur-

'nace area pairwof downwardly converging In general the furnace structure is fab; 1

the portion 22' adjacent the hopper 23 has a smaller flight than the portion 22" of the remainder of the screw conveyor. However, these differential portions of each screw conveyor are carried on the same shaft and turn at the same speed. This conveyor construction permits a full feeding of the hopper and as the material passes from the smaller flight 22 to the larger flight 22" it will be thinned out and will'be passed through the furnace in this condition thus permitting a better agitation during its travel through the furnace.

At the other end each of the conveyors deposits the material into a chute 24 which in turn deposits the material into an elevator 25 whereupon the material is carried upwardly and discharged through discharge aperture'26.

lVhile any preferred or desired driving means may be provided for the conveyors, I have illustrated the shafts of the twin conveyors-as provided with bevel gears27 driven by a shaft 28. This shaft is driven by a chain 29 connected to a speed reducer 30, which in turn is connected by means of a chain 31 to a variable speed device 32 driven through chain 33 by means of a motor or the like 34. The elevator 25 is also preferably provided with a screw conveyor (not shown) driven by gearing 35 connected by chain 36 with the variable speed device 32.

One. or more burners 37 are mounted in the wall 16 of theprimary chamber 19 in such a manner that the flame'thereof directly impinges upon the material being conveyed therethrough. These burners also heat the primary chamber and the hot gases pass down the adjacent refractory loaflle 18v and through the conveyor troughs and into the secondary chamber 20.

While various-types of burners may be employed I have found that particularly efficient results can be obtained with the use "of a burner of the type shown in my copendi-ng joint application Serial No. 466,311. The burners 30 are preferably so constructed as to provide a slight excess of fuel to thus produce a reducing atmosphere providing a nonoxidizing condition within the furnace.

The top wall 14: over the primary combustion chamber 19 is provided with an opening 38 normally closed by agravity safety door 39 hiueedly mounted as at 40. The purpose of this door is to relieve the pressure of gases which might. accumulate beyond a degree of safety in the primary chamber. This might occur from various causes but particularly so if the feed of the material though the furnace becomes so heavy as to prevent the escape of gas under the lower edges of the bafiles 18 through the conveyor troughs.

The secondary chamber 20 is provided with a stack 40' provided with a break 41. intermediate its length to retard the draft so that the efiiciency of operation of the secondary chamber will not be adversely affected. An auxiliary stack 42 which is connected to the main stack and to the elevator adjacent the upper end thereof will conduct to the main stacklany trapped gases that may be present inthe elevator.

The reference character 43 indicates an air manifold by means of which air under pressure ma-y'b'e introduced into the secondary chamber. A pilot light 44.- is also provided.

In the operation of the furnace the vapor or gas given off due to the volatilization of the oil-0n the chips or in the cutting compound where oils are present, are highly combustible when :mixed with air. The purpose of the air supplied byithe manifold 43 is to promote combustion in the secondary chamber and this combustion. is controllable through the amount of air introduced through this mani-.

fold. Constant ignition ofv the locally produced combustible mixture is maintained by the pilot i l and the heat obtained through this combustion in the secondary chamber readily preheats the material passing through the secondary chamber with the result that during continuous operation of the furnace it is possible to reduce the quantity of gas or fuel used in the burner 33? in the primary chamber- It has been found that carbon not formed in detrimental excess by reason of any over supply of fuels because the tem perature of the furnace atmosphere at this point in the secondary chamber is fairly hi gh and if anycarbonshould be formed the draft from the stack 40 carries light particles of carbon up the stack.

lin operation the chips, fabricated parts or ethermaterial to be dried is deposited in the hopper 23 and conveyed longitudinally through the furnace by the twin conveyors 22. The material upon entering secondary combustion chamber 20 is preheated and in sub sequently' passing through the secmidary chambergives off a vapor as its temperature is raised. In passing through the furnace this action increases until all of the volatile compound is removed. In the primary chamber 19 the temperature is higher than the vaporization point of any of the oil or cutting compounds so that prior to being discharged all oil. water, moisture or cutting compounds having oil as a base are removed. As previously mentioned the burners 87 produce a completely reducing atmosphere so that the materials being treated are uninjured through oxidation.

The material at the discharge end of the furnace is deposited through chute 24 to the elevator25 where it is discharged through the discharge opening 26.

Various modifications may suggest themselves to those skilled in this art and to this end reservation ismade to make such changes as may come within the purview ofthe accompanying claims.

\Vhat I claim as my invention is:

1. In a drying furnace of the character described having a heating chamber, means for dividing the heating chamber into a primary chamber and a secondary chamber, means for conveying the material to be dried through said chamber, a burner for heating said primary chamber to drive combustible gases from said material, and means for promoting combustion of said gases in said secondary chamber.

2. In a drying furnace of the character described having a heating chamber, means for dividing the heating chamber into a primary chamber and a secondary chamber, means for conveying the material to be dried through said chamber, a burner for heating said primary chamber, and means including a manifold for introducing air under pressure into said secondary chamber to promote combustion of combustible gases therein, as

and. for the purpose set forth. 7

In a furnace comprising a heating chamber for drying chips and the like, means for conveying the materialto be dried through the furnace, baflle means intermediate the heating chamber of the furnace dividing the same into a primary chamber and a secondary chamber, burners for heating said primary chamber, the gas resulting from the volatilization of oil on said chips being present in said secondary chamber, and means for promoting the combustion of said gases including a manifold for introducing air under pressure and a pilot light for maintaining said combustion, for the purpose set forth.

4. In a structure of the class described, a furnace comprising a heating chamber, means in said furnace dividing the heating chamber thereof into a primary chamber and a secondary chamber, a material conveyor extending through said chambers, a burner for heating one of said chambers, and means utilizing the gases of volatilization for promoting combustion in the other of said chambers.

In a device of the class described. a furnace having a heating chamber, baflie means intermediate said heating chamber for dividing the same into a primary chamher and a secondary chamber, burner means for heating one of said chambers and a gravity actuated safety device in the Wall of said latter chamber, for the purpose set forth.

6. In a chip drying furnace of the character described, a furnace structure including a heating chamber, a screw conveyor extending longitudinally therethrough, said conveyor having a portion extending beyond the furnace at one end thereof, this projecting portion of the conveyor havin a smaller flight than the remainder of t e conveyor and a hopper arranged above/the said projecting rtion of said conveyor, for the purpose set orth.

In testimony whereof I aflix my si ature.

FRANK H. LONGY AR. 

